The long range goal of this project is study of mechanisms of genetic exchange in Group A streptococci, emphasizing transduction and lysogenic conversion; and to investigate how altered or new genetic information can affect pathogenicity or other characteristics of these bacteria. Ongoing studies have shown production of an erythrogenic toxin (type B) by a non-lysogenic strain and production of a different toxin (type C) by this strain after lysogenization by a phage from a C-producing strain. These findings suggest that production of some erythrogenic toxins may be determined, as previously believed, by lysogeny; but that the genetic coding for others resides elsewhere than on prophage. Efforts to locate this site are in progress.